Memory-enhancing peptides and the use thereof

ABSTRACT

In this invention, chemical synthesis method has been used to improve the structure of memory-enhancing peptide. The animal experiments demonstrated that this kind of chemicals shows remarkable physiological activities, which may be helpful in ameliorating mental impediment in adults and promoting the intelligence development in adolescent, even can be a clinical medicine for the patient of Alzheimer&#39;s disease.

FIELD OF THE INVENTION

[0001] This invention relates to a synthesis of peptide and its analogs. Particularly, it focuses on the synthesis and application.

BACKGROUND OF THE INVENTION

[0002] It has been reported that arginine-vasopressin (AVP) have effect on the memory of animals but not show obvious influence on the learning process. Since AVP is a kind of hormone in vivo and its main function is in anti-diuretic process and to enhance blood pressure, it's not appropriate for the clinical therapy in enhancing memory. Therefore, on the basis of patent “memory-enhancing peptide and its application” (Chinese Patent No. ZL 93112493.X), we go on with work about the structural improvement and perform a series of pharmacological experiments, aiming to modify the defect in the existing patent and search for new memory-enhancing peptides which have simpler structure, stronger pharmacological activity, easy to produce, and have clinically curative effect on promoting the intelligence development in adolescent, ameliorating mental impediment in adults, accelerating the memory.

SUMMARY OF THE INVENTION

[0003] The purpose of the invention is to provide for a kind of memory-enhancing peptides which can ameliorate mental impediment in adults and promote the intelligence development in adolescent, even can be a clinical medicine for the patient of Alzheimer's disease.

[0004] Depending on the results of biological activity, we have designed a series of new chemicals with memory- and learning-enhancing function. Their structure general formula is as following:

[0005] X can be Ala; Leu; Ile; Cys; Phe; Tyr; Val;

[0006] R₁ represents PyroGlu; H;

[0007] R₂ can be S—S—C—(CH₃)₃; S—(CH₃)₃; R₂ is a kind of hydrophobic side-chain to stabilize spatial conformation of the whole molecule.

[0008] If R₁ is PyroGlu, R₂ is S—S—(CH₃)₃ or S—(CH₃)₃ or other groups which have hydrophobic side-chain to stabilize the spatial conformation of the whole molecule.

[0009] If R₁ is H, R₂ must be S—S—(CH₃)₃ or S—(CH₃)₃ or other groups which have hydrophobic side-chain to stabilize the spatial conformation of the whole molecule.

[0010] X can be Ala; Leu; Ile; Cys; Phe; Tyr; Val.

[0011] The peptides in this invention can be obtained through solid or liquid peptide synthesis method step by step. The synthesize protocol is as following:

[0012] The pharmacological tests of memory-enhancing peptide in this invention have been performed as following: the animals have been divided into three groups: drug administration group, control group and model group, with each group administrated with memory-enhancing peptide, saline and scopolamine respectively. In the test, the groups except control group were injected with scopolamine after the administration of medicine about 50 min., 10 min. later, the training began. First, the animals will be put into reaction box for 3 min. before each trails to familiarize them with the environment. Then, the reaction box are charged with 36V alternating current. When the animal subjects to electrical shock, it will jump up to the central platform to avoid harmful stimulation as a normal response. Most of animals may be return to the copper curdles twice or even more times, but they will jump back to the platform swiftly as the results of electrical shock. Each test trail will be performed for 5 min. and two following indices will be used to represent the learning results: (I) the number of total error (EN) during the whole training period; (2) the reaction time (RT) for the first returning to the copper curdle in the trail. The trails will repeat again 24 hrs later as memory test. The results as shown in Table 1 demonstrated that memory-enhancing peptide can remarkably ameliorate the memory and learning impediment induced by scopolamine.

[0013] Compared with model group, the memory-enhancing peptide at the dose of 0.5 μg and 1 μg/kg can obviously improve the memory and learning impediment induced by scopolamine, shown as longer incubation period and lesser error numbers which have marked difference from those of model group(P<0.01). In addition, memory-enhancing peptide (0.5 μg/kg and 1 μg/kg ) have better effects than Huperzine A (100 μg/kg ) in ameliorate the memory and learning impediment induced by scopolamine. TABLE 1 The effect of memory-enhancing peptide (MEP531) on the learning and memory process of mouse Drug dosage Scopolamine Learning Results Memory Results Group μg/kg mg/kg RT(s) EN RT(s) EN Control group Saline — 131.4 ± 98.3 0.9 ± 0.87 285.4 ± 22.6 0.4 ± 0.51 Model group Saline 1 27.5 ± 29.4^(♦♦) 2.3 ± 1.4^(♦) 140 ± 117^(♦♦) 1.9 ± 1.2^(♦♦) Huperzine A 100 1 120.5 ± 114.9* 1.3 ± 2.3** 231.9 ± 78** 0.9 ± 0.7** MEP-531 0.25 1 78.8 ± 118.7 0.3 ± 0.48** 197.6 ± 75.1 0.9 ± 0.56** MEP-531 0.5 1 241.6 ± 51.9** 0.2 ± 0.4** 245.5 ± 62.9** 0.5 ± 0.5** MEP-531 1 1 267.6 ± 31.4** 0.3 ± 0.5** 282.8 ± 33.4** 0.3 ± 0.5**

DETAILED DESCRIPTION OF THE INVENTION

[0014] Implement case 1

[0015] Chemical synthesis of Asn—Cys(Bu^(t))—Pro—Arg(MEP422)

[0016] Boc-system step-by-step solid phase synthesis method; Started from 2 g Merrifield resin.

[0017] The crude product described above was separated and purified through Silica gel column (Silicagel 60) initially and then subjected to C₁₈ HPLC for further purification. The elution time in HPLC is 19.1 min and solution system is TFA/acetonitrile system.

[0018] The results shown in the following table demonstrated the product has reasonable amino acid component. Experimental Asn: 1.05 Arg: 0.96 Pro: 1.08 Cys: not anlysis value Theory value Asn: 1.00 Arg: 1.00 Pro: 1.00 MS analysis: MW⁺ 544.3

[0019] The method described in the upper phase can also be applied to the synthesis of other analogs as X represents Ala; Leu; Ile; Phe; Tyr; Val respectively.

[0020] Implement case 2

[0021] Chemical synthesis of PyroGlu—Asn—Cys(S—Bu^(t))—Pro—Arg(MEP531) Boc-system step-by-step solid phase synthesis method; Started from 2 g Merrifield resin.

[0022] The upper crude penta-peptide preparation was separated and purified through Silica gel column initially and then subjected to C₁₈ HPLC for further purification. The elution time in HPLC is 19.5 min and solution system is TFA/acetonitrile system. The results shown in the following table demonstrated the products has reasonable amino acid component. Experimental value Asn: 1.01 Glu: 1.03 Arg: 0.96 Pro: 0.95 Cys: not anlysis Theory value Asn: 1.00 Glu: 1.00 Arg: 1.00 Pro: 1.00 MS analysis: MW⁺ 687

[0023] The method described in the upper phase also can be applied to the synthesis of other analogs as X represents Ala; Leu; Ile; Phe; Tyr; Val respectively.

1 16 1 4 PRT Artificial Sequence Peptide Fragments 1 Asn Ala Pro Arg 2 4 PRT Artificial Sequence Peptide Fragments 2 Asn Leu Pro Arg 3 4 PRT Artificial Sequence Peptide Fragments 3 Asn Ile Pro Arg 4 4 PRT Artificial Sequence Peptide Fragments 4 Asn Phe Pro Arg 5 4 PRT Artificial Sequence Peptide Fragments 5 Asn Tyr Pro Arg 6 4 PRT Artificial Sequence Peptide Fragments 6 Asn Val Pro Arg 7 4 PRT Artificial Sequence Peptide Fragments 7 Asn Cys Pro Arg 8 4 PRT Artificial Sequence Peptide Fragments 8 Asn Cys Pro Arg 9 4 PRT Artificial Sequence Peptide Fragments 9 Asn Ala Pro Arg 10 4 PRT Artificial Sequence Peptide Fragments 10 Asn Leu Pro Arg 11 4 PRT Artificial Sequence Peptide Fragments 11 Asn Ile Pro Arg 12 4 PRT Artificial Sequence Peptide Fragments 12 Asn Phe Pro Arg 13 4 PRT Artificial Sequence Peptide Fragments 13 Asn Tyr Pro Arg 14 4 PRT Artificial Sequence Peptide Fragments 14 Asn Val Pro Arg 15 4 PRT Artificial Sequence Peptide Fragments 15 Asn Cys Pro Arg 16 4 PRT Artificial Sequence Peptide Fragments 16 Asn Cys Pro Arg 

I claim:
 1. A kind of memory-enhancing peptides, characterized by its chemical structure formula which is shown as following:

X can be Ala; Leu; Ile; Cys; Phe; Tyr; Val; R₁ represents PyroGlu; H; R₂ can be S—S—(CH₃)₃; S—(CH₃)₃; a kind of hydrophobic side-chain to stabilize spatial conformation of the whole molecule.
 2. A kind of memory enhancing peptides according to claim 1, characterised in that: If R₁ is PyroGlu; R₂ is S—S—(CH₃)₃ or S—(CH₃)₃; or other groups which have hydrophobic side-chain to stabilize the spatial conformation of the whole molecule; If R₁ is H; R₂ is S—S—(CH₃)₃ or S—(CH₃)₃; or other groups which have hydrophobic side-chain to stabilize the spatial conformation of the whole molecule; X can be Ala; Leu; Ile; Cys; Phe; Tyr; Val.
 3. A kind of memory-enhancing peptides according to claim 1, characterised in that they are obtained through solid or liquid peptide synthesis method step by step.
 4. A kind of memory enhancing peptides according to claim 1, characterised in that their application on the preparation of medicine or health-care food which can ameliorate memory impediment and improve intelligence development on juvenile. 